96 PerrilliatRevista Mexicanaet al. de Ciencias Geológicas, v. 23, núm 1, 2006, p. 96-106 Upper Cretaceous (Cenomanian–Turonian) bivalves from northern Jordan, Middle East María del Carmen Perrilliat1,*, Fayez Ahmad2, and Francisco J. Vega1 1 Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510 México, D. F., Mexico. 2 Faculty of Natural Resources and Environment, Department of Earth and Environmental Sciences, The Hashemite University, P. O. Box 150459, 13115 Zarqa, Jordan. *[email protected] ABSTRACT Twelve species of bivalves are described for the Upper Cretaceous Ajlun Group of northern Jordan. The specimens were collected in three localities of the Fuheis (?middle to late Cenomanian), Hummar (late Cenomanian), and Shuayb (early Turonian) formations. Some of the species here described are reported for the fi rst time in Jordan and confi rm Tethyan paleobiogeographic affi nities. Key words: Bivalvia, Upper Cretaceous, northern Jordan, Middle East. RESUMEN Se describen e ilustran doce especies de bivalvos procedentes del Cretácico Superior del Grupo Ajlun en el norte de Jordania. Los especímenes fueron recoletados en tres localidades de las formaciones Fuheis (Cenomaniano medio? a tardío), Hummar (Cenomaniano tardío) y Shuayb (Turoniano temprano). Algunas de las especies descritas son reportadas por vez primera para Jordania y confi rman una afi nidiad paleobiogeográfi ca con la Provincia del Tethys. Palabras clave: Bivalvia, Cretácico Superior, norte de Jordania, Medio Oriente. INTRODUCTION Neumann (1999), Sabaheen and Mustafa (2000), and Ahmad and Al-Hammad (2002). Upper Cretaceous carbonate rocks cover about two- The aim of the present work is to study the bivalves thirds of Jordan. These rocks are rich in microfossils and from the Upper Cretaceous Fuheis, Hummar, and Shuayb invertebrates. During the Cenomanian and Turonian, Jordan formations, cropping out in Zarqa area (Figure 1). The was largely covered by shallow, warm seas. In this lapse Fuheis Formation (Table 1) overlies the Naur Formation of time, strata of the Ajlun Group (Naur, Fuheis, Hummar, and is overlain by the Hummar Formation throughout Shuayb, and Wadi As Sir formations) were deposited. most of north Jordan, with a maximum thickness of 80 m. Previous studies of these sediments concentrated mainly on It is composed of fossiliferous marl and marly limestone, the petrography, microfossils and occasionally macrofossils, and includes foraminifera, ostracods, gastropods and e.g., Bandel and Geys (1985), Powell (1989), Abed and echinoids (Wetzel and Morton, 1959; Basha, 1978; Dilley, Kraishan (1991), Aqrabawi (1993), Nazzal and Mustafa 1985). Bivalves reported from this formation include (1993), Shinaq and Bandel (1998), Bandel et al. (1999), Exogyra fl abellata, E. columba, Cardium sp., Neithea sp., Upper Cretaceous bivalves from northern Jordan, Middle East 97 Powell, 1989). The Shuayb Formation is early Turonian in age (Wetzel and Morton, 1959; Basha, 1978; Dilley, 1985), and is overlain by the Wadi As Sir Formation. It consists of thinly bedded limestone and marly limestone, which is mostly fossiliferous, including ammonites and foraminifera that support the age. Bivalves present in this formation include: Exogyra columba, E. conica, E. olisiponensis, Plicatula raynesi, P. forneli, Lucina useilli, and Cardium saportae (Powell, 1989). Other fossil groups present are dasycla- dacean algae, gastropods, ostracods, and echinoids. In central and southern Jordan, the Hummar Formation is absent, the base of the Shuayb Formation is not traceable, and the formation has been included in the undifferentiated Fuheis / Hummar / Shuayb unit. Powell (1989) assigned an early Turonian age to the Fuheis Formation. The bivalves were collected at three localities in the Figure 1. Location map of study area in northern Jordan. Black square area of Zarqua (Figure 2). Locality A (IGM-3513) includes indicates the area shown in Figure 2. outcrops of the Hummar Formation, and is found 3 km northwest of Urqub As Saqla (As Saqla Cliff), at 32º6’22” Lat N and 36º10’5” Long E. Locality B (IGM-3514) rep- resents the lithology of the Shuayb Formation in outcrops Pholadomya vignesi, Dosinia delettrei, Venus reynesi, Arca located 1.5 km east of Urqub As Saqla, at 32º5’2” Lat N trigeri, Protocardia moabitica and Cardium pauli (Wetzel and 36º15’35” Long E. Locality C (IGM-3515) is found and Morton, 1959). Oysters assigned to Rhynchostreon 1 km west of Jabal ar Ruhayd (ar Ruhayd Mountain) and mermeti (Coquand), and Amphidonte (Ceratostreon) fl abel- includes outcrops of the Fuheis Formation, at 32º6’19” Lat latum reinforced a ?middle to late Cenomanian age for this N, 36º16’5” Long E. formation (Aqrabawi, 1993). The studied material is deposited in the Colección The Hummar Formation is overlain by the Shuayb Nacional de Paleontología, Instituto de Geología, Formation, a prominent cliff-forming carbonate unit thin- Universidad Nacional Autónoma de México. Types are ning rapidly south of Wadi Mujib, Central Jordan. The included in the Type Collection and classifi ed under the formation consists of gray limestone, dolomitic limestone acronym IGM. The classifi cation herein follows that of and dolomite with a relatively poor macrofossil content. Vaught, 1989. Foraminifera and ostracods are present (Basha, 1978; Dilley, 1985), as well as corals, rudists and echinoids (Powell, 1989). Bivalves reported from this formation in- SYSTEMATIC PALEONTOLOGY clude Exogyra olisiponensis, Plicatula auressensis, Lucina sp., and Protocardia sp. (Wetzel and Morton, 1959). The Class Bivalvia Linnaeus, 1758 micro and macrofauna indicates a late Cenomanian age Order Arcoida Stoliczka, 1871 for this unit (Olexcon, 1966; Basha, 1978; Dilley, 1985; Superfamily Arcoidea Lamarck, 1809 Family Arcidae Lamarck, 1809 Genus Arca Linnaeus, 1758 Table 1. Upper Cretaceous stratigraphic units in northern Jordan. Type species. (International Commission on Zoological Group Stage Formation Nomenclature, Opinion 189, 1945): Arca noae Linnaeus. Belqa Coniacian–Santonian Wadi UmmGhudran Chalk Recent. Mediterranean Sea and Eastern Atlantic Ocean. Subgenus Eonavicula Arkell, 1929 Turonian Wadi As-Sir Limestone Shuayb Type species. Arca quadrisulcata J. de C. Sowerby, 1824. Ajlun Arca (Eonavicula) sp. Hummar Figures 3, 4, 5 Cenomanian Fuheis Description. Shell elongate, trapezoidal; hinge narrow. Naur Limestone Anterior margin rounded below, subtruncated above; ventral Lower Cretaceous Kurnub Sandstone margin slightly concave centrally; posterior margin sharply 98 Perrilliat et al. rounded. Sculpture of numerous radial prominent ribs and Genus Inoceramus J. Sowerby, 1814 interspaces of equal width. Type species. Inoceramus cuvieri J. Sowerby, 1814. Material examined. Nine articulated specimens. Senonian. England. Hypotypes. IGM 8846, length 62.4 mm, height 27.1 mm, ?Inoceramus sp. diameter 27.9 mm (both valves); IGM 8847, length 55.3 Figures 6-8 mm, height 28.5 mm, diameter 24.0 mm (both valves); IGM 8848, length 51.1 mm, height 25.5 mm, diameter 21.9 mm Description. Shell medium-sized, slightly inequivalve, (both valves). inequilateral, subovate to subcircular; moderately convex. Left valve slightly more infl ated than right one with slightly Occurrence. Shuayb Formation (early Turonian). incurved, prosogyrate beak. Anterior margin nearly straight, ventral margin semi-circular. Sculpture of fi ne commarginal Discussion. The specimens are internal molds similar to growth costae with narrow interspaces; faint radial lines. Barbatia (Plagiarca) carolinensis Conrad (1875, p. 4, pl. 1, fi g. 11) from the upper part of the Exogyra ponderosa Material examined. Three articulated specimens. zone in North Carolina, in shape and sculpture of shell; but the Jordanian specimens are larger in size. Hypotypes. IGM 8849, length 41.4 mm, height 35.4 mm, diameter 32.4 mm (both valves); IGM 8850, length 32.0 mm, height 29.4 mm, diameter 16.6 m (one valve). Order Pterioida Newell, 1965 Superfamily Pterioidea Gray, 1847 Occurrence. Fuheis Formation (Cenomanian), and Shuayb Family Inoceramidae Giebel, 1852 Formation (lower Turonian). Figure 2. Geologic map of study area. Localities indicated: A, locality IGM-3513, outcrops of the Hummar Formation; B, locality IGM-3514, outcrops of the Shuayb Formation; C, locality IGM-3515, outcrops of the Fuheis Formation. Upper Cretaceous bivalves from northern Jordan, Middle East 99 Discussion. The Jordanian specimens are similar in outline of left valve, seven strong radial ribs and sometimes with and ornamentation to Inoceramus virgatus Schlüter, 1877 remnant of spines, scally growth lamellae in whole surface described in Elder and Box (1992, p. 13, fi gs. 9.1, 9.2) from of shell; interior with oval adductor muscle scar. Right valve lower-middle Turonian of Alaska. subcirclar and with scally growth lamellae. Genus Mytiloides Brongniart, 1822 Material examined. Five specimens. Type species. Ostracites labiatus Schlotheim, 1813. Hypotype. IGM 8852, length 55.1 mm, height 68.4 mm, Turonian. England. diameter 46.0 m (left valve). ?Mytiloides sp. Occurrence. Fuheis Formation (late Cenomanian), Hummar Figure 9 Formation (early Turonian), Shuayb Formation (early Turonian). Description. Shell medium-sized, trapezoidal, equivalve, inequilateral, moderately prosocline; slightly convex with Discussion. Complete synonymy of this species can be seen poorly differentiated umbo and terminal beak that barely in Malchus, 1990, p. 134. protudes beyond dorsal margin; hinge line short; fl anks